This invention relates to a formed alumina body and to a method for manufacturing the same, particularly, to an improved porous alumina body and an alumina compound material.
An alumina ceramic material has excellent hardness, mechanical strength, heat resistance and chemical stability. The heat resistance thereof is not inferior to other ceramic materials such as silicon carbide and silicon nitride. In addition, alumina ceramic materials are inexpensive. Therefore, alumina ceramic materials are widely used as industrial ceramic materials as described by Japanese Published Patent Application No. 54-87716.
Alumina ceramic products are conventionally made by forming fine alumina particles in desired shape and then firing the formed shape, or forming and firing fine alumina particles at the same time as described by Japanese Published Patent Application No. 57-95870 or Japanese Patent Publication No. 59-25748. In conventional alumina ceramic materials, a matrix is formed of alumina particles simple shapes.
Conventional alumina ceramic materials have the following disadvantages:
(1) The workability is bad due to their hardness.
(2) The shock resistance is weak because of their brittleness. Generally speaking, the shock break resistance of alumina ceramic materials is inferior to that of metals.
(3) It is difficult to form products with complex shapes exactly.
(4) The firing temperature is a high temperature on the order of 1500.degree. C. to 1900.degree. C.
(5) The shrinkage on firing is large.
(6) The thermal shock resistance is low.
(7) The lubricity is poor compared with that of metals.
Because of these disadvantages, although alumina ceramic materials have many excellent basic characteristics, they cannot be used satisfactorily as structural materials which must satisfy severe strength and mechanical reliability requirements.